Case Study #5

C62xx C54x

# of channels 30 30

(V.34 modem datapump)

# of channels / DSP 15 3

# of DSPs 2 10

DSP total cost $192 $330

$ / channel $6.40 $11.00

mW / channel 200 mW 40mW

Space / channel 82mm2 65mm2

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This case study follows the format of previous ones by looking at the tradeoffs associated with power dissipation, cost, performance. It is by looking at these attributes that will help determine whether this is a C54x or a C6x socket. Other factors, like coding methodology, could come into play. Since this particular customer has not used DSP before, they may be reluctant to code in assembly. If this is the case, while the C54x has an excellent C Compiler, the C6x is the leader in ease of use and efficiency with respect to assembly. In this case, the task is to implement 30 channels which would require ten 100 MIPS C54x’s, each handling 3 channels. The total processor cost is $330, which translates to $11.00 per channel. The mW / channel is 40 mW ((115 mW x 10) / 30 = 38.3 mW). The space required is 65 mm2 computed by ((14 mm x 14 mm) x 10) / 30. The C6x can handle 15 modems per 6201 which means that two 6201s would be needed to handle the E1 span (30 channels). The total C6x processor cost is $192, the cost per channel is $6.40, the power per channel is 200 mW, and the space is 82 mm2. As the graphic shows, the C6x is definitely the better choice from the cost per channel perspective. The power per channel and the space per channel are very comparable to the C54x. As a result, for the modem portion of this application would best be suited as a C6x application.